Returns the intersection of this set with the other set

Property definitions

core $ Set :: intersection
	# Returns the intersection of this set with the `other` set
	fun intersection(other: Set[E]): Set[E]
	do
		var nhs = new_set
		for v in self do if other.has(v) then nhs.add(v)
		return nhs
	end
lib/core/collection/abstract_collection.nit:515,2--521,4